Coil Problem?

[gsmoke]

2.0 a/c
This problem all started with backfiring when slowing down, this got worse with intermittant loss of power. When it starts its undrivable, but most times of trying theres been no spark.
Fuel is getting through no problem , so plugs, leads, distributer cap and rotor arm have been swapped around and individually checked. The coil's primary and secondary resistance are within limits so I thought that it must be the ignition module.
I've bought a new one and the van started fine though still backfiring badly. Now I've just tried to start it this morning and I've got no spark again. .
Could this annoying problem be caused by the coil even though it tests ok?
Thanks
gsmoke

[AngeloEvs]

Not an exper on a/c but coils generate high voltages and even though the coils read Ok when measuring the resistance the insualtion between the coils and casing could be breaking down. If you are satisfied that you have checked everything then either test it or get a another would be my advice. A coil is just a simple transformer, one side goes to 12V and the other side of the primary coil is intermittently grounded by the ignition module. If your not getting a spark off the secondary then either the voltage is leaking somewhere, the coil isn't grounding via the igntion module or you ain't got 12V to the coil in the first place.

[jason k]

geraint have you tried bypassing the idle stabilisation unit??

these can give funny running conditions

[gsmoke]

Yes, thanks Jas.
This van is making me go mental.
Thanks for your replies.

[jason k]

an iffy coil will give those conditions you describe too